GB2066037A

GB2066037A - Multiple reusabel tubular casing

Info

Publication number: GB2066037A
Application number: GB8035778A
Authority: GB
Original assignee: Ashland Food Technology Holdings SA
Current assignee: Ashland Food Technology Holdings SA
Priority date: 1979-11-09
Filing date: 1980-11-07
Publication date: 1981-07-08
Also published as: DK473780A; ES8203009A1; KR830001098B1; JPH0115251B2; ES8301590A1; AR225644A1; AU6373880A; US4371554A; ATE4952T1; ES496659A0; EP0028858B1; ES507461A0; US4437206A; EP0028858A1; JPS5692729A; KR830003881A; KR830002784B1; BR8007280A; FI803485L; DD154189A5

Description

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SPECIFICATION

Multiple reusable tubular casing, and apparatus and process for using same in the production of caseless 5 (skinless) parboil or raw sausages

This invention relates to apparatus and process for making caseless (skinless) sausage. In particular,

this invention relates to a particular reusable tubular 10 casing and associated apparatus for making parboil or raw sausage.

In general, the art recognized three types of sausages: cooking sausage, parboil sausage, and raw sausage. Cooking sausage has a higher fat and pro-15 tein content and accordingly contains a smaller amount of water than the parboil sausage. Forthis reason cooking sausage releases practically no water during the heating process, and can therefore be produced in casings that are impenetrable by 20 water vapor and steam evolved during the sausage-making process. For example, many organic polymeric materials that are impervious to water and steam, can be used with cooking sausage.

On the other hand, a larger amount of water is 25 released during reddening and coagulation of the parboil sausage, and during the reddening and ripening process for raw sausage.

Parboil sausage is produced from an emulsion in water of a protein and fat. During the formation of 30 this emulsion in high capacity grinding or cutting machines, ice is used for cooling. Forthis reason, the bulk sausage contains more waterthan is permiss-ibleforthe preservation, of the sausage. Therefore, the bulk sausage must release about 5 to 50% (as an 35 average about 10%) gaseous constituents, in relation to the raw (unprocessed sausage meat) weight.

These gaseous constituents consist forthe most part of water vapor or steam, but also contain aromatic constituents and other volatile substances released 40 during the heating steps for reddening and/or coagulation.

The reddening of parboil sausage occurs as a rule at about 35°C within approximately 15 minutes; the coagulation must be carried out at temperatures 45 above 45°C and takes place as a rule by heating in water or steam at temperatures between 70 and 100°C, usually at about 80°C, in a relatively short time.

Almost all parboil sausages are smoked. It is a 50 general practice to complete the smoking process after reddening, but before coagulation. Since the sausage casings in use at the present time have little . permeability for smoke, the smoking process normally takes a longtime.

55 Raw sausage is produced from bulk sausage which contains fat and meat pieces of various size. During the reddening and ripening process the bulk sausage releases gaseous constituents from about 10 to 50%, as related to the raw (unprocessed bulk) 60 weight. These gaseous constituents also consist for the most part of water vapor, however, they also contain aromatic constituents and substances volatile under the conditions of the reddening and/or ripening process.

65 The reddening and ripening of raw sausage occurs at temperatures not above 40°C, as a rule at around 20°C. The reddening and ripening occurs quite slowly during the course of a few days up to several months. Some types of raw sausages are also smoked. In the reddening and ripening process for others, as for instance salami, mildew (mold) is expected to form.

In original sausage making procedures, the bulk sausage was injected into a natural intestine and subsequently subjected to the treatment required by a particulartype of sausage. Artificial intestines made of various materials have been known for quite some time. Most of the natural and artificial intestines used for sausage casings are inedible and must be removed before consumption. Therefore, it has become the practice to peel the sausage casing right at the production plant.

Anothertechnique has been used in sausage making, namely the production of so-called caseless sausages (also designated as skinless sausages), in order to reduce the expense incurred in peeling the sausage casings, the loss of sausage material because the sausages break when the casings are peeled away, and, in addition, the quite sizable cost of the casings themselves.

According to German Patent Publication DE-OS 25 23 506, caseless sausages are produced continuously by a machine that is provided with numerous molds, which after removal of the formed and cooked sausage, and after cleaning of the mold, can be used again. One by one these molds pass thru a fill station in the machine; a boiling or, as the case may be, a cooking oven; a cooling station; and a mold removal station, whereby between the mold removal station and the following fill station preferably a wash and/or cleaning station is provided. The molds are preferably made of a material having a low coefficient of friction, for instance "tetraf-luoroethylene". This designation obviously is to mean "polytetrafluoroethylene". It is, however, in no way indicated that the material used forthe molds could be or were required to be pervious for gas.

German Patent Publication DE-OS Number 27 56 995 refers to a process and apparatus forthe production of a skinless, chord-like sausage by means of a hull designed as a chord-shaped hollow body which is designated expressly as "practically medium-tight" or "practically medium-tight sealable". The inside of the hollow body may have a smooth anti-sticking layer which, for instance, could be a coating fcf polytetrafluoroethylene. According to the process described in DE-OS 27 56 995, the raw bulk sausage is filled into the casing, then heated, possibly followed by cooling, and finally divided into suitable lengths. The pressure created during heating due to the expansion of the bulk sausage causes a pressure seal which prevents vapor evolved during cooking to reach the casing exit.

It is also known that a special paper made into an endless tube can be impregnated with viscose (a viscous solution of cellulosexanthogenate, which is used forthe production of viscose rayon, viscose staple fibers, viscose cellophane and viscose sponges), to form a tubular casing which has a degree of porosity which permits the exchange of

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moisture and steam. Such viscose impregnated paper tubes can be used for sausages that are to be smoked, because their permeability allows for some penetration of smoke, at least to a degree that 5 exceeds the smoke penetration of most other known sausage casings. Experience has shown that all known multiple reusable but nonporous casings are not suitable forthe production of sausage types which must release water vapor, steam and other 10 gaseous constituents. It is, of course, not possible to remove the water vapor, steam and other gaseous constituents from the sausage material before filling.

Also, a previous effort to use a finely perforated sausage wrapper having a large number of holes per 15 square centimeter proved to have severe shortcomings with respect to providing a smooth outer sausage surface, and presented cleaning problems.

A multiple reusable porous casing forthe production of caseless parboil or raw sausages must meet 20 the following requirements:

1. The casing must have a sufficiently high permeability for water vapor, steam and other gases,

like oxygen and aromatic constituents. A cellulose material which, however, is suited for one time use

25 only and is not part of the present invention, may release for instance 5.5 /jl\ of water vapor or steam per minute per square centimeter. Similar characteristics are desirable for multiple reusable casings.

2. The casing, even by multiple reuse, must

30 neither release constituents injurious to health nor may it adversely affect the taste, smell or appearance of the sausage.

3. The pores must not, or at least only to a small degree, become plugged with fat, so their permeabil-

35 ity is not decreased.

4. The casing must be easy to clean.

5. The casing must have a continuous thermal tolerance of at least 200°C.

6. The casing must have good mechanical stabil-40 ity and be pliant.

7. The casing must not adhere to the bulk sausage.

8. The internal surface of the tubular membrane must contain openings that are small enough so that

45 the sausage's integral external surface has a smooth appearance.

The invention involves the discovery that a porous polytetrafluoroethylene (PTFE) membrane with a microstructure comprising PTFE nodes which are 50 connected with each other by PTFE fibrils, is suited forthis purpose. This material can be produced having small fibril lengths to yield effective pore sizes no more than 1.0 /im, preferably no more than 0.5 jim, and optimally no more than 0.2 mm. It is preferred 55 that the membrane have a nominal thickness of 0.01 to 5 mm and a nominal porosity of 30 to 99, and preferably 55 to 85%. Membranes of this type, their characteristics and production, are known from U.S. 3,953,566 and U.S. 3,962,153 as well as the corres-60 ponding German Publications DE-AS 21 23 316 and DE-OS 2417 901; therefore, they need not be described in detail.

The PTFE membrane of the casing of the present invention has sufficient porosity to permit venting 65 radially through the casing, the steam, water vapor and other gaseous fluids released during processing from the sausage present within the casing. The PTFE membrane also has a surface texture to provide easy release of the processed sausage from the casing following processing while maintaining the integrity of the sausage surface and the sausage as a whole. Furthermore, the gaseous fluid flow paths through the node and fibril microstructure of the membrane limits the extrusion of solid or liquid sausage material through the membrane during filling of the casing, thus preserving the desired high degree of porosity and low adhesion between the sausage material and casing inner wall.

As used in U.S. 3,953,566 and as defined herein, porosity is equal to the void fraction of the PTFE membrane expressed as a percentage. That is, porosity Q is equal to void fraction times 100, where void fraction + polymer fraction = 1.

The void fraction fv can be calculated from the specific gravity of the membrane as follows:

where SG is the specific gravity of the porous PTFE membrane, and SGP is the specific gravity of the PTFE polymer, and is generally equal to about 2.15 Thus, the porosity can be determined from the following relationship:

Q-1-5| „00)

The required permeability forthe evolved gas (water vapor, steam, aromatic constituents, etc.) for a certain type of sausage and at a particular temperature is easily calculated with near accuracy, if one a) assumes that the specific gravity of the raw bulk sausage is equal to 1,

b) does not take into account the existing sausage ends,

c) knows the amount of waterto be released percentage-wise (%) in relation to the raw bulk sausage, and d) knows the time available forthe release of the gases at the particular temperature.

Given these prerequisites the volume Vw of the sausage therefore is:

Vw = 7TR2L

and the surface area Owof the sausage is: s

Ow = 2 7TRL

where R is the radius and L is the length of the sausage. If the amount of waterto be released redesignated as Pw in percent (%), in relation to the raw bulk sausage, and the time available forthe release of the gases at a given temperature T is designated as tT, the permeability for gas at a temperature T is as follows:

7tR2L x Pw _ R x Pw 2 77ft L x tT 2t^

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Therefore it follows that the bigger the radius of the sausage, and the largerthe amount of waterto be released, the higherthe gas permeability must be; and the gas permeability can also be that much smaller the more time that is available for the release of gas.

A porous PTFE membrane suitable forthe production of parboil sausage, like hot dogs, Vienna sausages, frankfurters, Lyon sausage, Mortadella and so on, has the following characteristics:

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a) effective size of pores b) nominal thickness c) nominal porosity d) nominal density e) air permeability maximum 0.2/j.m

0.0033 inches 78%

0.4 g/cm3

minimum 215 cm3 per minute and per square inch at 4.88 inches of head of water maximum 120 seconds minimum 40 pounds per square inch (40 p.s.i.) minimum 13,

maximum 22 p.s.i. (pounds per square inch) maximum 28 seconds

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f) the time required for 500 cm3 of methanol to pass thru 9.6 cm2 area 25 of the membrane at21°C and a vacuum of 27 inches of mercury (Hg):

30 g) water entry pressure h) bubble point (methanol)

35 i) the time required for 100 cm3 of air to pass thru 1 square inch of the membrane area 40 at 4.88 inches of head of water

Measurements (e) and (i) are typically done with the apparatus and procedure detailed in ASTM 45 Method D-726-58 Method A using 1.00 sq. inch test area, and 4.88 in. head of water. The measurement in (i) represents the "Gurley Number" of the membrane.

Measurements (f) and (h) are typically done with .50 the apparatus and procedure detailed in ASTM

Method F-316-70, using anhydrous methanol at 21 °C and a 9.6 sq. cm test area.

Measurement (g) utilizes apparatus employed in the Mullin's BurstTest (Fed. Std. 191, Method 5512). 55 The test procedure consists of raising the pressure of waterto a test level over a period of approximately 10 seconds, holding the pressure atthat level for30 seconds, and visually determining the presence or absence of leakage. The lowest water pressure at 60 which leakage is observed is the Water Entry Pressure of the membrane.

A preferred range of porous PTFE membrane is as follows:

thickness:

weight/area: density:

70 Gurley No.:

Bubble Point Pressure:

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Water Entry Pressure:

0.0015"-0.0035"

(.04 mn-.Q9 mm)

2.79-4.03 mg/cm2

0.44-0.63 g/cm3

(corresponds to a porosity of about 70-80%)

28 seconds maximum, any measurement

13 psig minimum, any measurement

15.6-22 psig, average of any eight measurements

40 psig minimum, any measurement

This membrane is also suitable for the production 80 of raw sausage, like cervelat or salami sausage; in view of the fact that the release of gas in the case of raw sausage occurs at lowertemperatures over a longer period of time, the permeability of the membrane may be smaller.

85 By the term "membrane" is meant a relatively thin soft pliable free-standing sheet and no specific limitations insofar as the length and width are intended.

The casings may be seamless tubes or can be produced from flat stock as for instance by heat or 90 ultrasonic welding, by gluing or sewing. For example, a band-like membrane may be wound helicoi-dally into a tube. The casing may consist wholly or forthe most part of the above-designated membrane.

95 It is preferable, for reasons of the mechanical load capacity, that the casing is supported by reinforcing components contacting at least a fraction of its surface area.

The polytetrafluoroethylene membranes, when 100 used in accordance with the invention, are food-technologically unobjectionable, thermally stable between -20 and +250°C, resistant to diluted acids and lye solutions as well as common cleaning agents, and are not changed by the effects of 105 ultrasonic and microwaves. The use of these membranes makes it possible to change the production method of parboil and raw sausages, as compared with the customary process, in an advantageous manner.

Up to now, machines were used to fill the casings with the bulk sausage. The filled casings were lined up on a spit and then one after another subjected in the smoke chambers to, in sequence:

reddening drying smoking cooking or parboiling cooling

After leaving the smoking chambers, the sausage 120 casings may be removed by peel machines in order to produce "skinless" sausages. Forthis process a relatively large amount of manual labor is required.

The capital investment of an installation forthe production of sausages with multiple reusable cas-125 ings depends mainly on the period of time required forthe sausage to remain in the casing;

therefore this time must be kept to a minimum.

A portion of the time required forthe reddening

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process should therefore preferably take place before the bulk sausage enters the casing. The smoking can be done after the shaped, coagulated and cooled sausage is ejected from the casing because 5 the reddening and coagulating steps provide a thin integral skin on the sausage that enables the sausage to be handled. The release of water vapor, steam and other gaseous constituents, however, must occur at the beginning of the heating cycle while the 10 sausage is still in the membrane casing. Microwave heating is ideally suited for shortening the reddening and coagulation steps.

The production of parboil sausage according to the present invention can proceed as follows: 15 a) The raw bulk sausage is pre-reddened in a mixing machine under exclusion of oxygen.

b) The bulk sausage is filled, according to invention, into reusable casings and/or devices that are formed by a water-vapor permeable membrane

20 that is pliable, heat stable and non-adherentto bulk sausage by means of fill machines, paste fill machines or dividing machines.

c) The filled casings or devices are then heated to approximately 35°C to attain a desired degree of

25 redness in a continuous reddening apparatus as, for example, by convection heating.

d) Subsequently the filled casings or devices are heated for the coagulation step to about 80°C, as, for instance, in the customary way by steam or

30 hot air or specially advantageously by means microwave energy which so far, to the knowledge of the inventor, has not been used forthis purpose.

e) Next, the filled casings or devices are cooled, for 35 example, by means of cold water, cold air, liquid oxygen, etc.

f) Now the casings or devices are opened by automatic removal of the end caps, after which the sausage is ejected, for instance, by compressed

40 air. The empty casings are returned in a closed cycle to the fill station, whereby in suitable intervals cleaning takes place, as for instance by ultrasonic waves.

g) The sausages are subsequently either continu-45 ously or intermittently smoked, on appropriate conveyors or special racks having only a small contact area with each sausage. The tanning effect of the smoke essentially contributes to the integrity of the sausage.

50 h) Subsequently the sausages are cooled and are ready for shipment.

The following describes preferred embodiments of the apparatus and process forthe production of caseless sausage, as shown on the attached draw-55 ing.

FIG 1 shows a simplified sectional view of the end portion of a device made in accordance with the present invention forthe production of sausage.

FIG 2 is a simplified perspective view of the device 60 shown in FIG 1.

FIG 3 is a perspective view of the retaining ring portion of the device.

FIG 4 is a vertical section of the device with the upper part removed.

65 FIG 5 shows a cross-section of the end segment of the completely assembled device.

FIG 6 is an exploded view in perspective of a structural detail.

FIG 7 shows the complete device in simplified 70 perspective.

FIG 8 is a front view of the device.

FIG 9 is a longitudinal cross-section of a variation of the device shown in FIG 1 but still made in accordance with the present invention.

75 FIG 10 shows the variation of FIG 9 in perspective.

FIG 11 shows a cross-section of the end segment of yet another version ofthedevfce shown in FIG 1.

FIG 12 is an exploded view in perspective of a version shown in FIG 11.

80 FIG 13 is a section along plane Xlll/XIII of the version shown in FIG 12.

In accordance with the present invention, as embodied herein and with reference to FIG 1, there is provided a reusable tubular sausage casing 5 of a 85 porous polytetrafluoroethylene (PTFE) membrane, the details of which were discussed earlier. Tubular casing 5 is shown in the shape of a hollow right circular cylinder but the scope of the present invention is not intended to be so limited. Tubular casing 5 90 is shown positioned in the interior of support structure 1 which will discussed henceforth.

In accordance with the invention, and as embodied herein, there is provided means for supporting the reusable casing at its outside surface. A 95 preferred device incorporates a support structure designated in its entirety by 1, which is composed of parallel longitudinal ribs 2, and ring-shaped cross ribs 3 in a lattice arrangement. The lattice structure 1 is designed in two parts, that is, it is divided into 100 practically equal halves along a parting plane designated E in FIG 2. The two halves are connected along the parting plane by screws 4 for possible disassembly (compare in this connection also FIG 4). The longitudinal ribs 2 and cross ribs 3 are aligned with their 105 inside edges along an imaginary cylinder which corresponds to the diameter of the sausage to be produced. Inside the lattice structure 1 a tube-like casing 5 which is made of the above defined porous PTFE membrane is fastened to the lattice structure 1 at its 110 end sections by retaining rings 8. Forthis purpose the ends of the longitudinal ribs 2 are provided with a circular groove 6 which matches and/or engages the shoulder 7 of retaining ring 8 (FIG 3).

The outermost end section of the retaining ring 8 115 is shaped into a circular flange 9. Preferably, the retaining ring 8, as FIG 1 shows, is divided into two equal halves 8a/8b, for ease of assembly. The end section of the casing 5 is easily fastened to the latticp structure 1 by pushing the two retaining ring halves 120 8a/8b into it until the circular shoulder 7 snaps into the groove 6 thus capturing the casing end therebetween.

During the process the bulk sausage 10, as depicted in FIG 5, expands underthe effect of heat 125 and subsequently contracts again during cooling. In accordance with the invention, means for restraining the sausage material within the tubular casing and for compensating forthe change in volume of the sausage is provided and is shown in FIGS 5 to 8. 130 As embodied herein, and as shown in FIG 5, a

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floating piston 11 is positioned within the retaining ring 8. Piston 11 is provided at one end with a concave face surface 11a whose shape matches the contour of the sausage to be produced. A cylindrical 5 guide sleeve 11b is adjacent to the piston face surface 11a, which in a preferred design only glides on the inner surface area of the retaining ring 8 and thus does not even come in contact with the easily vulnerable casing 5. An insert designated by 12 carries a 10 plastic coil spring 13 on the side facing the piston 11, which rests against the curved wall of piston 11, and according to FIG 5, tends to press or bias the piston to the right. Thus it is assured that the piston always rests against the outer area of the sausage 10 and 15 that changes in volume of the bulk sausage are automatically compensated by the elasticity of the spring 13.

The bushing 12 is practically cup-shaped like a pot and has on its vertically arranged circular flange (as 20 shown in FIG 5) two key-hole-like slots with which it can be mounted for removal in customary fashion on studs 14 of the lattice structure. In this way it is sufficient to put the bushing 12 with the slots 15 having their wider section aligned overthe stud 14. By 25 turning bushing 12 slightly, the stud 14 securely engages the bushing.

As FIG 6 shows, the piston is provided with a guide pin 16 in the center part of its curved face surface 11a which, during insertion of the bushing 12, engages 30 with a bored hole 17 in the bushing and thus provides a secure alignment of the two parts.

The invention can be altered in numerous ways by any person skilled in the art, as for instance, it is of course not necessary to support the casing 5 around 35 its circumference by a lattice structure, but some type of pipe with a solid but porous wall could be used as well. A pipe of this type could preferably consist of a porous, non-metallic, air pervious material, for instance, sintered glass. In this case, retaining 40 parts forthe removable attachment of the casing 5 would also have to be provided for both end sections.

If the sausage 10 is to be removed from the described device, it is sufficient to take off bushing 45 12 and piston 11, and eject the sausage from the casing 5 by compressed air. The casing 5, which remains in the device, is washed and reused in the following manufacturing process.

It would also be possible to design the above--50 mentioned pipe in form of half-cylindrical shells (not shown) which are fastened to an endless conveying device (not shown) and are joined to form a complete pipe forthe support of the casing 5 shortly before introducing the bulk sausage. Forthe removal 55 of the sausage the half-shells could be parted again by the conveyor system.

Instead of the curved face surface 11a of the piston 11, a flat surface could be used advantageously for a sausage which is to be sliced before it is sold. In this 60 configuration, no waste is created during slicing.

In FIG 9, which depicts another device made in accordance with the present invention, the device has a pipe 18 which may be formed of sintered stainless steel, or preferably of a porous, non-metallic air 65 pervious material (for example, sintered glass). A

tube-like casing 19 of porous PTFE membrane, as described before, is laid around the pipe 18 as to completely encase the inner and outer surface of the pipe with the casing ends 19a/19b turned back and 70 overlapping each other on the outer surface of the pipe where they are welded together in a circular bead 20.

FIG 9 depicts in dashed lines how the one casing end 19b is turned back around the end section of the 75 pipe 18 in the direction of the arrow until it overlaps the other casing end 19a.

Another variation of apparatus made in accordance with the present invention and shown in FIG 11 includes a pipe 21 which, for instance, can be 80 formed of stainless steel or an adequate artificial material such as polyamid or sintered, unstretched polytetrafluorathylene, and provided with numerous holes. A porous PTFE casing 23 of the type defined above is turned back around the flanged end 21 a of 85 the pipe 21 at the position 23a and thus secured at the pipe end 21a by stretching overthe flange.

A cap 24 is divided in the direction of the circumference into several retaining fingers 25 (also compare FIG 12), which are mounted on a circular rib 26 90 and can pivot lever-like on their mounting point. The end 25a of each retaining finger 25 which is turned toward the inside engages in its end position a support flange 27 on the pipe.

A recess 28 in the rib 26 houses a coil spring 29 95 whose opposite end is compressed against the curved face 30a of the piston 30. The cylindrical sleeve 30b of the piston 30 which is adjustably positioned in a corresponding section 26a of the rib 26 as well as in the pipe 21, could however also be 100 placed (in orderto protect the casing) in section 26a only, in this way the piston 30 is resiliently pressed or biased against the end of the bulk sausage and thus balances the expansion and contraction of the bulk sausage as shown by the two arrows.

105 With its guide sleeve 26b pushed overthe end section of a guide bar which is part of the piston 30, the cap 24 functions as a centering and guiding device forthe piston 30. As demonstrated in the lower portion of FIG 11, the cap 24 can be disengaged and 110 pulled off, if need be, by depressing with finger pressure.

The spring 29 not only serves forthe compensation of changes in volume of the bulk sausage 31, but also exerts an oppositely directed force on the cap 115 24, so that the end of the retaining finger 25a is

"forced against the support flange 27; simultaneously the end of the retaining finger 25a also can exert a pressure in a radial direction which contributes to holding the casing 23 in place in a modification (not 120 shown) to the embodiment in FIG 11 wherein the turned back end of casing 23 extends past flange 27.

As FIG 13 shows, the cap 24 essentially consists of a heavy-walled tube made of synthetic material and whose wall is provided with several parallel slots 32 125 which are directed radially toward the inside.

Parboil sausages typically have diameters of from 15 to 200 mm, some of them also more. For instance, a small sausage weighing 55 g and having a diameter of 22 mm can be heated by microwaves to 35°C 130 for 15 minutes forthe process of reddening and

Claims

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ripening, and to 80 C for3 minutes forthe coagulation. Thereby the raw bulk sausage releases 5 g of steam in the course of 18 minutes.

Should the coagulation take place by means of 5 microwave energy, the casings and/or devices used must not contain any metallic constituents. In this case the support components of the device advantageously consist of perforated synthetic materials like polyamide or sintered unstretched polytetraf-10 luoroethylene.

The coagulation process by means of microwaves can take place in such a way where the filled casings and/or devices are passed thru a stream of microwaves at a set cycle. While passing thru the mic-15 rowaves, the casings and/or devices are turned as described later, in order to assure an even heating. Heat is not applied from the outside, but is produced simultaneously and nearly evenly throughout the entire mass of sausage, so that coagulation 20 advances from within to the outside.

Heat generation in the bulk sausage starts instantly at actuation of the microwave energy and stops just as abruptly when turned off. Since no heat transfer mediums need be heated with microwave 25 apparatus and only extremely little heat is dissipated to the environment, significant energy conservation is possible.

During microwave heating, the various components of the bulk sausage, namely water, fat and pro-30 tein, are heated to different degrees. In addition, because the energy absorption is dependent on the temperature on account of the temperature dependence of the dielectric constant, local (spot) overheating may take place. To avoid this, microwave 35 heating is advisably applied periodically in order to allow the temperature of the bulk sausage mass to become balanced. Good results are obtained when the duration of the first heating period amounts to no more than 50 seconds, the duration of the follow-40 ing heating periods is shortened by 30% each, and the duration of the heating intervals, starting at 10 seconds, be increased until the heating intervals match the heating periods. The heating intervals can be obtained by using multiple sources of mic-45 rowaves with a specific distance between each source along the process path. In such application, it is advantageous to position between the microwave sources a different type of heating unit, for instance, infrared heating, is used, in order to avoid the cool-50 ing of the bulk sausage and to further accelerate coagulation.

The selection of power output of the microwave sources is of great importance for fast and even coagulation. Although the speed of coagulation is 55 accelerated by increased power output, the evenness of the coagulation decreases. On the other hand, too small a power output is uneconomical on account of too slow a production speed. However, it is easily possible for an expert to determine the 60 proper parameters.

Rotation of the filled casings and/or devices during the microwave heating process is indispensable since adjoining casings shield or block each other from the microwaves. The period of rotation should 65 be shorter by more than one order of magnitude than the period required for coagulation. This amounts to at least about 12 revolutions per minute.

The new casing, apparatus, and process of the invention provide a sausage that has far superior resistance to bacterial contamination than sausages produced in the usual water-vapor-impervious, one-use, cellulosfc casings, which is the present industry standard for frankfurter production.

Because the smokfng step can be performed on the sausage itself, with no cellulosic membrane of varying permeability to smoke, the tanning effect of the smoking step is moreuniform and provides superior resistance to bacteria. Also, there is no possibility of cutting into the sausage during a peeling step, which could destroy the integrity of the sausage skin and permit bacterial access to the interior of the sausage.

The invention permits use of a faster sausage making procedures (microwave) in the reddening and coagulation steps. Also, the smoking step can proceed at a much faster rate, because there is no bar-rierto the smoke such as exists when a cellulosic casing ts used. The invention permits production of sausages with less laborthan the use of cellulosic casings, indeed, the invention permits manufacture of sausage without contact with human hands. CLAIMS

1. A sausage casing capable of multiple reuse for the production of caseless sausages, the casing comprising a tube formed of a porous polytetrafluoroethylene (PTFE) membrane, said membrane having a microstructure made up of nodes interconnected by fibrils, said PTFE membrane having sufficient porosity to permit venting radially through said tube the steam, water vapor and other gaseous fluids released during processing from the sausage present within said tube, said PTFE membrane also having a surface texture to provide easy release of the processed sausage from said tube following processing while maintaining the integrity of the sausage surface and the sausage as a whole, the gaseous fluid flow paths through the node and fibril microstructure of said membrane limiting the extrusion of solid or liquid sausage material through the membrane during filling of said tube, said PTFE membrane also having

(i) a Gurley No. of about 1 to 650 seconds, as determined per ASTM Method D-726-58 Method A using a 1.00 sq. inch test area, 4.88 in. head of water, and represents the time in seconds to flow 100 cm3 of air through the test area,

(ii) a Bubble Point pressure of about 3 to 60 psig, as determined per ASTM Method F-316-70, using anhydrous methanol at 21 "C and a test area of 9.6 sq, cm., and

(iii) a Water Entry Pressure of about 7 to 600 psig, as determined by the following procedure: using the apparatus employed in the Mullin's Burst Test (Fed. Std. 191, Method 5512) the pressure of water is raised to a test level over a period of approximately 10 seconds, hefd atthat level for30 seconds, and the lowest presence or absence of leakage is visually determined, the Water Entry Pressure being the pressure level at which leakage is determined to occur.

2. The casing as in claim 1 wherein the Gurley

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No. has a maximum value of about 28 seconds in any measurement and the maximum of the average of any eight Gurley No. measurements is about 20 seconds; wherein the Bubble Point Pressure is about 5 13 psig minimum for any measurement and the average of any eight Bubble Point Pressure measurements is about 15.6 to 22 psig; and wherein the Water Entry Pressure is greater than about 40 psig.

3. The casing as in claim 1 or 2 wherein said tube 10 is formed by aflat band of said PTFE membrane wound helicoidally and joined atthe adjacent band edges.

4. The casing as in claims 1,2, or 3 wherein said PTFE membrane has a thickness of about 0.01 mm to

15 5 mm, and a porosity of about 30 to 90%, the porosity Q being defined as follows:

Q = L1"2^ (100)

20

where SG is the specific gravity of said PTFE membrane.

5. The casing as in claims 1,2, or 3 wherein said PTFE membrane has a thickness of about 0.04 to 0.09

25 mm, and a porosity of about 70 to 80%, the porosity Q being defined as follows:

Q = L1-2^ (100>

30

where SG is the specific gravity of said PTFE membrane.

6. A casing as in claim 1 having the following characteristics:

(a) a thickness of about 0.003 inches;

(b) a porosity Q of about 78% where

Q = t1-2§fe (100)

40 and SG is the specific gravity of the PTFE membrane;

(c) density of about 0.4 g/cm3;

(d) a maximum Gurley No. of about 28 seconds, as determined per ASTM Method D-726-58 Method A

45 using a 1.00 sq. inch test area, 4.88 in. H20 pressure drop, and represents the time in seconds to flow 100 cm3 of air through the test area;

(e) a minimum Bubble Point Pressure of about 13 psig and a maximum of about 22 psig, as deter-

50 mined per ASTM Method F-316-70, using anhydrous methanol at21°C and a test area of 9.6 sq. cm;

(f) a Minimum Water Entry Pressure of about 40 psig, as determined by the following procedure:

using the apparatus employed in the Mullin's Burst

55 Test (Fed. Std. 191, Method 5512) the pressure of the water is raised to a test level over a period of approximately 10 seconds, held atthat level for30 seconds, and the presence or absence of leakage is visually determined, the Water Entry Pressure being the low-60 est pressure level at which leakage is determined to occur; and

(g) a time required for 500 cm3 of methanol to pass the test area using the apparatus and procedure detailed in (e) of about 120 seconds.

65 7. A sausage casing capable of re-use forthe production of caseless sausage as claimed in claim 1, substantially as described herein.

8. Apparatus forthe production of caseless sausage comprising a tubular casing formed of porous 70 polytetrafluoroethylene (PTFE) membrane, and support means in contact with the outer surface of said tubular casing, said PTFE membrane having a microstructure comprising nodes interconnected by fibrils, said PTFE membrane having sufficient porosity 75 to permit venting radially through said casing the steam, water vapor and other gaseous fluids released during processing from the sausage present within said casing, said PTFE membrane also having a surface texture to provide easy release of 80 the processed sausage from said casing following processing while maintaining the integrity of the sausage surface and the sausage as a whole, the gaseous fluid flow paths through the node and fibril microstructure of said membrane limiting the extru-85 sion of solid or liquid sausage material through the membrane during filling of said casing, said PTFE membrane also having

(i) a Gurley No. of about 1 to 650 seconds as determined per ASTM Method D-726-58 Method A

90 using a 1.00 sq. inch test area, 4.88 in. head of water, and represents the time in seconds to flow 100 cm3 ofairthroughthe test a rea,

(ii) a Bubble Point Pressure of about 3 to 60 psig, as determined per ASTM Method F-316-70, using

95 anhydrous methanol at21°C and attest area of 9.6 sq. cm., and

(iii) a Water Entry Pressure of about 7 to 600 psig, as determined by the following procedure: using the apparatus employed in the Mullin's Burst Test (Fed.

100 Std. 191, Method 5512) the pressure of water is raised to a test level over a period of approximately 10 seconds, held atthat level for30 seconds, and the presence or absence of leakage is visually determined, the Water Entry Pressure being the lowest 105 pressure level at which leakage is determined to occur.

9. The apparatus as in claim 8 wherein the Gurley No. has a maximum value of about 28 seconds in any measurement and the maximum of the average 110 of any eight Gurley No. measurements is about 20 seconds; wherein the Bubble Point Pressure is about 13 psig minimum for any measurement and the average of any eight Bubble Point Pressure measurements is about 15.6 to 22 psig; and wherein the 115 Water Entry Pressure is greater than about 40 psig.

' 10. The apparatus of claim 8, wherein said tubular casing includes a flat band of said PTFE membrane helicoidally wound and joined atthe adjacent band edges.

120 11. The apparatus of claim 8 wherein said PTFE membrane has a thickness of about 0.01 mm to 5 mm and a porosity of about 30% to 90%, the porosity Q being defined as follows:

125 Q = [1 -|^J (100)

where SG is the specific gravity of said membrane.

12. The apparatus as in claim 8,9,10 and 11, 130 wherein said PTFE membrane has a thickness of

8

GB 2 066 037 A

8

about 0.04 mm to 0.09 mm, and a porosity of about 70% to 80%, the porosity Q being defined as follows:

5 Q-ll-|||000)

where SG is the specific gravity of said membrane.

13. The apparatus as in claim 8, said porous PTFE membrane having the following characteristics:

.jq (a) a thickness of about 0.003 inches;

(b) a porosity Q of about 78% where

Q = [1 ~2^1(100)

15 and SG is the specific gravity of the PTFE membrane;

(c) density of about 0.4 g/cm3;

(d) a maximum Gurley No. of about 28 seconds, as determined per ASTM Method D-726-58 Method A

20 using a 1.00 sq. inch test area, 4.88 in. H20 pressure drop, and represents the time in seconds to flow 100 cm3 of air through the test area;

(e) a minimum Bubble Point Pressure of about 13 psig and a maximum of about 22 psig, as deter-

25 mined per ASTM Method F-316-70, using anhydrous methanol at 21°C and a test area of 9.6 sq. cm;

(f) a minimum Water Entry Pressure of about 40 psig, as determined by the following procedure: using the apparatus employed in the Mullin's Burst

30 Test (Fed. Std. 191, Method 5512) the pressure of the water is raised to a test level over a period of approximately 10 seconds, held atthat level for 30 seconds, and the presence or absence of leakage is visually determined, the Water Entry Pressure being the low-

35 est pressure level at which leakage is determined to occur; and

(g) a time required for 500 cm3 of methanol to pass the test area using the apparatus and procedure detailed in (e) of about 120 seconds.

40 14. The apparatus of claims 8,9,10,11,12 or 13, wherein said support means includes a lattice structure having a plurality of longitudinal ribs arranged in a cylindrical pattern to surround the outer surface of said casing and oriented parallel to the axis of said

45 casing; a plurality of ring-shaped cross-ribs cooperating with said longitudinal ribs to restrain radial movement of said casing surface and spaced along the axis of said casing; and means for securing the respective ends of said casing to the respec-

50 tive ends of said support means.

15. The apparatus as in claim 14, wherein said securing means includes a pair of retaining rings each provided with a shoulder on its outer peripheral surface, and wherein said plurality of cross-ribs

55 include at least two cross-ribs positioned one at each respective end of said support means and each having a circumferential groove in the inner peripheral surface for receiving the shoulder of a respective retaining ring, the respective end of said casing

60 being captured therebetween.

16. The apparatus as in claim 15, further comprising combined means for restraining sausage material disposed within said casing for processing in respect to axial movement of the sausage material

65 and for compensating for volumetric changes of the restrained sausage material during processing, said combined means including at least one piston supported by one of said retaining rings for sliding axial movement, an end of said piston contacting the sausage material and having a shape corresponding to the desired contour of the sausage end, and resilient means for biasing said piston end against the sausage material.

17. The apparatus as in claims 15 or 16, wherein each of said retaining rings comprises at least two ring segments.

18. The apparatus as in claim 16 or 17 wherein the shape of said piston end is substantially flat.

19. The apparatus as in any ofclaims 8 to 13, wherein said support means includes a cylindrical support member comprising at least two member segments separable along a plane, the axis of said casing lying within said plane, and means for joining said segments in the area of the plane of separation.

20. The apparatus as in any of claims 8 to 13, wherein said support means includes a porous pipe having an inner peripheral surface conforming to and surrounding the outer surface of said casing and means for securing the casing to said porous pipe.

21. The apparatus as in claim 20 wherein said porous pipe is formed from sintered glass.

22. The apparatus as in claim 20 or 21 wherein the ends of said casing extend beyond the respective edge of said pipe and wherein said securing means includes a pair of annular flanges disposed about the outer peripheral surface of said pipe, one proximate each end thereof for receiving the ends of said casing turned back on themselves to stretchingly overlap said flanges.

23. The apparatus as in claim 20 wherein the apparatus further comprises combined means for restraining sausage material disposed within said casing for processing and for compensating for volumetric changes in the restrained sausage material during processing, said securing and restraining means including an annular support flange positioned on the outer peripheral pipe surface at at least one end of said pipe, at least one end cap having a plurality of flexible retaining fingers disposed in the axial direction around the periphery of said cap, the retaining ends of said retaining fingers radially moveable into and out of engagement with said flange, a piston supported by said cap for sliding axial movement, an end of said piston contacting the sausage material, and resilient means cooperate ing with said cap for biasing said piston end against the sausage material.

24. The apparatus as ir» claim 20 or 21, wherein, the ends of said casing extend beyond the ends of said porous pipe and when turned back on themselves overlap on the outside surface of said pipe, and wherein said securing means includes a ring-shaped weld-bead joining the overlapped portions of said casing ends.

25. Apparatus forthe production of caseless sausage, substantially as hereinbefore described with reference to and as shown in Figures 1 to 8,9 and 10 or 11 to 13 of the accompanying drawings.

26. A process forthe production of caseless sausages, the process comprising the steps of filling

70

75

80

85

90

95

100

105

110

115

120

125

130

9

GB 2 066 037 A

9

reusable tubular casings formed of a vapor-permeable porous membrane having a microstructure of nodes interconnected by fibrils, said membrane being pliant, heat stable, and non-adherent to 5 bulk sausage with unprocessed sausage material; reddening the sausage material to a desired degree of redness by heating the filled casings;

coagulating the bulk sausage material by continued heating of the sausage material, said reddening and

10 coagulating steps including the concurrent steps of venting radially through the porous casing excess steam, water vapor, and other gaseous constituents released by the sausage material during said reddening and coagulating steps; ejecting the coagulated

15 sausage material from the porous casings, the integrity of the membrane being maintained during said ejection step; and cleaning said reusable casings for subsequent refill with unprocessed sausage material.

20 27. The process as in claim 26, wherein said membrane is highly porous polytetrafluoroethylene.

28. The process of claim 26 or 27, in which the ejection step includes pneumatically ejecting the coagulated sausage material in a substantially axial

25 direction.

29. The process as in claim 27 or 28, wherein the casing is positioned in a casing support means and the casing and the casing support means are non-metallic, and said reddening and coagulating steps

30 include the step of irradiating the casing and contained sausage material with microwaves.

30. The process as in any one of claims 26 to 29, wherein said cleaning step includes the step of exposing the casings to ultrasonic waves.

35 31. The process as in any one of claims 26 to 30 further including the step of pre-reddening the unprocessed sausage material no less than the desired degree of redness, said pre-reddening step occurring priorto the filling step.

40 32. The process as in any one of claims 26 to 31, for making parboil sausages, wherein the reddening step includes heating the filled casings to a temperature of about 35°C and the coagulating step includes heating the sausage material to about 80°C.

45 33. The process as in any one of claims 26 to 32 further including the step of smoking the coagulated sausage material after the ejecting step.

34. The process as in any one of claims 26 to 33, which is carried out using apparatus as claimed in

50 anyoneofclaims8to25.

35. A process forthe production of caseless sausages as claimed in claim 26, substantially as described herein.

36. A caseless sausage which has been produced

55 by the process as claimed in any one of claims 26 to

35.

Printed for Her Majesty's Stationery Office by TheTweeddale Press Ltd., Berwick-upon-Tweed, 1981.

Published atthe Patent Office, 25 Southampton Buildings, London, WC2A1AY, from which copies may be obtained.